In aerostatic bearings, air from an external air source is fed, under pressure, through one or several throttle openings or nozzles in a clearance between two cooperating bearing surfaces. The fed air creates air cushion having a pressure sufficient to support a load. The pressure in the bearing clearance is sharply reduced from pressure P.sub.1 at the nozzle edge to an ambient pressure P.sub.a at the bearing edge. Therefore, to increase the carrying capability, the number of nozzles should be increased. However, the increase of the number of nozzles should be effected without a substantial increase of the manufacturing costs. The chambers and channels which define separate nozzles, which serve for distribution of air in the bearing clearance and thereby influence the increase of the carrying capability, are dimensioned with regard to flow characteristics defining the air flow through the nozzle. The drawback of conventional aerostatic bearings with such chambers and channels consists in that these chamber and channels have a dead volume which increases the tendency of the bearing to self-exciting oscillations.
So-called porous bearings, formed of porous air-permeable material have a large number of separate micronozzles. The micronozzles or air-permeable points are uniformly distributed over the bearing surface providing for a uniform pressure profile along the entire bearing clearance and, thereby, insuring a high carrying or support force. In these bearings, the narrowest cross-section of the micronozzles are not located directly in the bearing surface and, therefore, they have, as the bearings with channels and chambers, a dead volume unfavorable to a dynamic operation. For this reason, methods were developed according to which the porous material on the bearing surface was either purposefully compressed to a certain layer thickness (German Patent No. 3,439,648) or completely closed (German Publication No. 3,230,232) in order to subsequently open this layer in a desired manner. The required processes are difficult to implement, especially, when a predetermined flow resistance of the nozzle layer should be provided and a uniform distribution of nozzle points over the bearing surface need be insured. A compacted porous bearing, in which the compacted layer is again partially open by using a laser, is disclosed in European publication EP-A-0237627. The opening of the layer, or forming the nozzles therein, is effected from the bearing clearance side, which results in worsening of flow characteristics.
Treatment of metals with a laser is described in numerous publications. For example, drilling with a laser is described in an article of Yukitaka Nagano "Laser Drilling" in a ASM Engineering Bookshelf," 1978, pages 115-121. In a book of George Chryssolouris "Laser Machining" on page 209, use of laser drilling for producing "aerosol nozzles" is described. However, the aerosol nozzles referred therein are not nozzles of an air bearing, which should insure the provision of specific flow characteristics.
Different air bearings are disclosed in U.S. Pat. No. 3,600,046 and German Patent No. 3,001,061. In the disclosed bearings, the nozzles have a conical shape. In the bearing disclosed in German Patent No. 3,001,061, grooves are provided on the side of the bearing clearance which adversely affect the dynamic behavior of the air bearing.
In the magazine "Mechanical Engineering," June, 1961, pages 45-48, there is disclosed a bearing to the improvement of which the present invention is directed. In the bearing described therein, the micronozzle region is formed as a foil in which the microholes are formed with a needle mechanically.
Accordingly, an object of the invention is an aerostatic bearing having good static and dynamic characteristics and which can be manufactured at a relatively low cost.